Presently about 6.8 M tons of soybean is produced in India and extracted for oil and the solvent extracted flour is exported for feed purposes. By providing additional facilities for the hygienic processing of soybean in the solvent extraction units, it is possible to obtain edible grade defatted flour having the desired functional characteristics. After the recovery of oil, 4.9 M tons of soy flour is available for utilization in India. As a by-product of edible oil production, oilseed proteins are a potentially important source of human dietary protein throughout the world. Following oil removal, the protein present in the defatted cakes is heat-denatured and therefore directly un-extractable. Hence, proteolysis is an attractive approach for recovering the protein from cake in soluble form and affords a high protein preparation suitable for protein fortification of a wide variety of foods. A small portion of total soybean produced also finds use for different edible grade flours, protein isolate and texturized products and popularity of these products are greatly picking up globally. Soybean is an excellent source of protein, which contains about 40% protein. New manufacturing techniques for high quality soybean foods have been developed by lowering or destroying of the anti-nutritional factors like trypsin inhibitors.
U.S. Pat. No. 5,180,597 sets forth a process for hydrolyzed vegetable protein with enhanced flavor, which contains no detectable level of monochlorodihydroxypropanol. In the above reference, wheat gluten is hydrolyzed using Prozyme 6 (a fungal protease) at a temperature of 40–50° C., pH 6.5–7.0, with an enzyme concentration of 0.1–2.0% of substrate for a time period of 4 h. The hydrolyzed protein is treated with gaseous HCl for deamidation before the addition of acid for inactivating the enzyme. The drawback in such hydrolysis is that it is likely to lead to racemisation of amino acids and the addition of acid increases the salt content in the product.
Reference may be made to Ernster, J. H. (1991), U.S. Pat. No. 5,077,062, Excelpro Inc., Los Angeles, Calif. USA, wherein a low sodium, low mono sodium glutamate soy hydrolysate that is prepared from soy material such as soy flour, soy meal or soy grits using fungal protease in water is described. The hydrolysis is conducted in the absence of acid or base at 90° C. for 2 h. After deactivating the enzyme and de-watering the mixture the resulting hydrolysate contains between 45 and 55 wt. % enzymatically hydrolyzed soy based protein with an average molecular weight of 670,000±50,000. The fungal protease used is different from the enzyme used in the present invention. Such single enzyme systems are likely to result in bitter peptides and the process is energy intensive due to the high temperature (90° C.) used.
Reference may be made to Satoh et al., (1988) U.S. Pat. No. 4,757,007, Nisshin Oil Mills, and Tokyo, Japan wherein the method describes preparation of two hydrolyzed products using a protease from soy protein. The soy protein is hydrolyzed with papain or pepsin after precipitating with alcohol. The drawback of the process is it involves the separation of the mixture of hydrolyzed products. Hydrolysis is carried out using papain or pepsin. Acidification is carried out to bring down the pH to 2.5–5.0 to separate the two kinds of hydrolysates, which could lead to increase in salt content.
Reference may be made to Cipollo, K. L. and Wagner, T. J., (1987) European Patent No. 0148600 B 1, Ralston Purina Co., wherein the described process relates to the preparation of hydrolyzed protein from protein isolate after jet cooking or dynamic heating at 104° C. for a few seconds and later cooled in a vacuum chamber before hydrolysis using bromelain. The protein was precipitated at its isoelectric point from an aqueous extract of the material before the hydrolysis. The drawback of the process is the starting material protein isolate which is expensive. The process is a multi-step process, energy intensive. The process further needs machines like the jet cooker and a vacuum chamber.
Reference may be made to Parker, D. M. and Pawlett, D. (1987) European Patent No. 0223560 A2, Imperial Biotechnology Ltd., wherein the method describes the separation of protein hydrolysates with meat and cheese flavor, from proteinaceous feed stocks (e.g. containing soybean, gluten, whey, casein, hemoglobin, yeast, cereal or microbial proteins) by stepwise hydrolysis using an endopeptidase followed by amino peptidase from Streptococcus lactus. The drawback of the process is it is a multi-step process.
Reference may be made to Lee, (1986) European Patent No. 0087246 B1, Staffer Chemical Co. wherein a process for the hydrolysis of soybeans, wheat gluten and cotton seeds using fungal protease from Aspergillus and pancreatin (trypsin, chymotrypsin A, B and C, elastase and carboxypeptidase A and B) is described. Activated charcoal is used to treat the hydrolysate, which is used for nutritional improvement. The draw back of the process is that it involves many more steps.
Reference may be made to a Boyce, C. O. L. et al. (1986) European Patent No. 0187048 A2, NOVO Industries A/S, wherein a process is described for the preparation of soy protein hydrolysate with 0.25 to 2.5% degree of hydrolysis (DH) using microbial rennet (Mucor miehei) and to be used as an egg white substitute. The enzyme used in this process is different and involves a low degree of hydrolysis of soy protein.
Reference may be made to Olsen, H. A. S. (1981), United Kingdom Patent No. 2053228A, wherein a process for the production of soy protein hydrolysate from partially defatted soy material by hydrolysis with proteolytic enzyme. The drawback of the process is that due to partial defatting soy flour, left over oil comes in contact with protein phase, which could lead to off-flavors.
Reference may be made to Olsen, H. S. (1981) U.S. Pat. No. 4,324,805, wherein method described for producing soy protein hydrolysate and oil from partially defatted soy material by hydrolysis with proteolytic enzyme. The soy flour is partially defatted by water washing at pH 3.5–4.5 and later hydrolyzed using water and a base to increase the pH. The degree of hydrolysis (DH) is in the range of 8–12%. Oil is recovered from the wash water. Alcalase is the enzyme used. The drawback of the process is that it is a multi-step process and, due to partial defatting of soy flour, left over oil comes in contact with protein phase which could lead to off-flavors. Enzyme inactivation is done by addition of acid, which is likely to lead to increased salt content in the product.
Reference may be made to Sherba and Steiger (1972), U.S. Pat. No. 3,640,725, wherein enzymatic hydrolysis process for production of soy protein hydrolysates is described. The soy seeds are comminuted and heated at 90–140° C. Protease (fungal and bacterial) is added at 25–75° C. The fiber is separated and slurry has two phases—oil and aqueous phase. Aqueous phase is brought to pH 4.5 to precipitate the protein, which is then concentrated. The starting material is not defatted and hence the residual oil could come in contact with the aqueous phase, which could lead to off-flavors.
Reference may be made to Gunther, R. C. (1972) Canadian Patent No. 905742, wherein soy protein hydrolysate is modified with pepsin to yield a product, which, in presence of water and sugar, whips at a rapid rate to produce aerated products of low density.
Reference may be made to Tsumura, K. et al, (1997) European Patent No. 0797928 A1, wherein a process for the manufacture of a soy protein hydrolysate with a protease used selectively to decompose glycinin at a pH of 1.5–2.5. The pH used in the process is very low and therefore differs from the pH used in the present invention. Further, the aim of the process is to achieve a low glycinin content, which is not the case in the present invention.
Reference may be made to a published paper entitled “Industrial Production and Application of Soluble Enzymatic Hydrolysate of Soy Protein”, by Olsen, H. S., Adler Nissen, J. (1979), Process Biochemistry, 14(7), 6,8, 10–11, wherein a method for the preparation of soy protein hydrolysate from soy flakes washed at pH 4.5 followed by hydrolysis using alcalase is described. The solubility of the substrate is low at the acidic pH which is likely to result in low yields. The enzyme used is different from the enzyme used in the present invention.